Liquid level indicator



Dec. 21, 1948.

L. W. BURCH LIQUID LEVEL INDICATOR Filed July 30, 1943 BY came? {12% nwszvnm Lyndon \J. Burch.

QTTURNEYS.

Patented Dec. 21, 1948 UNITED STATES PATENT OFFICE LIQUID LEVEL INDICATOR Lyndon w. Burch, I )etroit, Mich. Application July 30, 1943, Serial No. 496,697

(Granted under-.the act of March 3, 1883, as

amended April so, 1928; 370 o. G. 757) Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The present invention pertains to a novel temperature-sensitive indicator operating on the principle that the resistance of a conductor varies with its temperature. In the simplest embodiment the conductor is merely exposed to the air or other medium and functions as a heat detector. In a more developed form the device is used for showing the liquid level in the fuel tank. In this application, use is made of the additional phenonemon that a conductor carrying current and exposed to both liquids and gas dissipates its heat of resistance to these media at diil'erent rates.

These principles are embodied in the level indicator by suspending a conductor in the receptacle and passing current therethrough. Asolenoid is electrically connected to the conductor and positioned to act upon a movable indicator. Variations of the liquid level will produce variations in the resistance of the circuit, the amount of current passed therethrough and the effect of the sonably accurate readings of the liquid level may be obtained.

In the preferred construction, the indicator is influenced by two opposed solenoids on opposite sides thereof, one of which is connected to the coil as previously stated. The other is connected in a manner to exert a. substantially uniform effect on the indicator and is preferably coupled with a. coil designed to balance the first named conductor and thus maintain the indicator in a neutral position during a given condition of the liquid level.

The invention is disclosed by way of example in the following description and in the accompanying drawing in which:

Figure 1 is a vertical section of a tank equipped with the invention as a level gage, and a wiring diagram of the apparatus.

Figure 2 is a detail section of a modified construction. 4

With reference to Figure 1, the tank or receptacle I contains a body of liquid 2, the level of which is to be indicated. In the tank is mounted a vertical perforated tube 3 preferably flanged at 4 over the top of the tank and'secured to said top by rivets 5. Upon the tank and over the tube is mounted a cap 6 for a purpose that will presently be described. The cap may be held by rivets I.

A pair of inverted binding posts 1 and 8 are mounted in the top of the cap 8 and insulated therefrom'by suitable bushings 9 clamped by nuts it) on the post. From the post I is suspended an insulating rod H passing centrally through the tube 3 to the bottom of the tank i.

The indicating instrument, which may be disposed at any suitable distance from the tank i, includes a magnetic needle or pointer i2 pivotally mounted at i3 and cooperating with a dial it. At opposite sides of the needle l2, preferably at the shorter lever arm, are disposed solenoids I 5 and 16 having their inward ends joined by a conductor H. The latter is connected to one terminal of a battery l8 or other source of current, the other terminal being grounded at l9. Each solenoid contains a soft iron or equivalent core 20.

The remaining end of the coil I5 is joined by a conductor 2! to the binding post I. An open coil '22 of conducting wire is wound on the insulating rod H, with its upper end secured at 23 to the post 1 and its lower end grounded through the tank i at 24. The wire may consist of pure iron, nickel or gold. Some alloys also are suitable for the purpose. The perforated tube 3 serves as an anti-splash guard for the coil 22. The remaining end of the coil is is connected by a conductor 25 to the binding post 8.

A dry coil 26 is disposed within the cap 8 has one end connected at 21 to the post 8 and its other end grounded through the cap at 28. The coil is separated from the cap by an insulating lining 29.

The electrical system comprises two circuits. One circuit may be traced from ground I! through the battery l8, coil I8, conductor 25, binding post 8, dry coil 26 and ground 28. The resistance of this circuit is fixed. The second circuit may be traced from ground I! through battery 18, coil l5, conductor 2!, binding post I,

coil 22 and ground 24. The resistance of this- I circuit varies with the depth of immersion of the coil 22 in the liquid 2.

The latter condition is due to the fact that the The system may be designed to pass equal currents through the coils l5 and I6 when the tank is half full, in which case the solenoid attracts the needle l2 with equal force on both sides and brings it to the mid-point of the scale I or in a vertical position. At this condition, the wire 22 is of the same resistance as the coil 26, so that the wire is balanced by the coil. When the tank is full, the temperature and resistance of the coil 22 are decreased, the current in coil l5 increased, and the needle I! moved to the right on the scale l8.

Figure 2 shows a modified form oi. liquid-permeable tube surrounding the sensitive wire. An insulating rod 3|, corresponding to the rod ll of Figure 1, is wound with a temperature-sensitive wire 32 as previously described, but preferably embedded in the rod at least flush with the surface thereof. This structure is enclosed in a series of superimposed tubes or sleeves 93 consisting of a porous ceramic material. A nonabsorbent washer 34 is preferably inserted between successive tubes. This construction replaces the perforated tube; of Figure 1.

The porous material permits the liquid to make contact with the wire 3| for the purpose previously described, with substantially no air at the wire so that the danger of combustion is entirely eliminated. The washers 34 prevent the absorbed fluid from risin by capillary action a substantial distance above the actual liquid level in the tank. The tubes may be molded on the rod, wire and washers if desired.

Although specific embodiments oi the invention have been illustrated and described, it will be understood that various alterations in the details of construction may be made without departing from the scope of the invention as indicated by the appended claims.

What I claim is:

1. In a liquid level indicating system wherein means is provided for electrically indicating the extent to which a resistance element is immersed in liquid, a resistance element comprising an insulating rod adapted to be mounted vertically in a receptacle containing liquid, a conductor supported along said rod and having a temperature coeflicient of resistance, and a porous ceramic material encircling said rod and conductor.

2. A liquid level indicator comprising, in combination with a receptacle, a cap mounted on said receptacle, an insulatin rod extending from said cap vertically into said receptacle, a conductor supported along said rod and having a temperature coeilicient of resistance, a coil mounted in said cap, two solenoids connected respectively to said conductor and said coil, a movable indicator mounted to be moved by said solenoids, and means for passing current through said conductor, coil and solenoids and connected to said sole holds in a manner to cause them to act opp sitely on said indicator.

3. In a liquid. level indicating system wherein means is provided for electrically indicating the extent to which a resistance element is immersed in liquid, a resistance element comprising an exposed temperature-sensitive conductor and porous liquid-permeable material fitted on said conductor.

4. In a liquid level indicating system wherein means is provided for electrically indicating the extent to which a resistance element is immersed in liquid, a resistance element comprising an exposed temperature-sensitive conductor, superimposed tubes of porous liquid-permeable material fitted on said conductor, and non-absorbent washers inserted between adjacent tubes.

5. In a liquid level indicating system having an indicator actuated by opposed solenoids, a liquid receptacle element comprising a cap adapted to be mounted on a receptacle, an insulating rod extending vertically downward from said cap, a conductor supported along said rod and having a temperature coefficient of resistance, a resistance element mounted in said cap, means for electrically connecting the conductor to one of the opposed solenoids, and means for electrically connectingthe resistance element to the other 'of the opposed solenoids.

LYNDON W. BURCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 989,420 Reichel Apr. 11, 1911 989,929 Schroder et a1 Apr. 18, 1911 1,459,391 Clausen June 19, 1923 1,681,314 Vawter Aug. 21, 1928 1,841,341 Tanner Jan. 12, 1932 1,957,510 Vawter May 8, 1934 2,181,960 Bacon Dec. 5, 1939 2,342,553 Olpin Feb. 22, 1944 FOREIGN PATENTS Number Country Date 7,288 Great Britain Mar. 27, 1913 129,741 Great Britain July 24, 1919 366,663 Great Britain Feb. 11, 1932 513,427 Great Britain Oct. 12, 1939 

